Few people realize the dark spiritual side of acting going all the way back to the Greek theater. The best actors in Greek theater were believed to be literally possessed by the entities they sought to portray on stage. Many occultists, like Aleister Crowley, taught that acting and assuming the role of a particular demon was the fastest way to come into contact with a demonic entity. Many actors and actresses have credited their success to possession by a spirit entity. Robin Williams claimed that when acting he becomes possessed, and that in the past they would have burned him as a witch. New Ager, Shirley McClain, has also admitted spirit possession when acting. Matrix star, Keanu Reeves, states that he attempts to connect with his muse and goes on what he refers to as “demon rides” when acting. Johnny Depp has claimed that he is possessed with a multitude of demons and Denzel Washington claims that he is able to put out such great performances because he gets on his knees and calls on spirits to possess his body and empower him to play a given role. Oprah Winfrey has claimed that she lights candles and then petitions spirits to possess her so that she can better perform as well. “I tried to empty myself and let the spirit of Sethe inhabit me,” admits Winfrey. Director, Jonathon Demme, who directed the movie Beloved, said of Winfrey's performance, “Oprah had explained to me when we originally met that it was her goal and intention to channel the spirit of Margaret Garner...This very infusion of humanity past accounts to a significant degree for Oprah's stunning alchemy, her astonishing abandonment of self in her Beloved performance.”

The evidence for a spiritual reality is overwhelming when one examines the preponderance of evidence found in mass testimonies by those in high places acknowledging influence from spirit entities. Add to this the fact that many of these actors like Oprah Winfrey are leading people into occult teachings that are forbidden by God through books like, The Secret and The New Earth. Sadly, many went away after viewing "The Dark Knight" reveling in Ledger's dark performance as the Joker and never realizing that they themselves may have fallen victim to yet another Hollywood movie glorifying evil.

The phenomenon isn't entirely fictitious, but I deny it's demonic and I deny it's possession. While writing novels and screenscripts, I have, like many writers, had characters "come to life", evince traits I hadn't known were in them, do things I didn't expect them to do, and send things in an unknown but inexorable direction - all with a singular internal consistency. Perhaps it's what Victorians used to call unconscious cerebration. In all events, it happens, and no, you don't go to Hell for it. It's a part of the creative process every artist devoutly hopes for.

I don't care if they strip naked and bark at the moon, doesn't mean that there really are any dark magic powers.

But frankly, I think you're reading way too much into what those actors said, even if that's a true recount of their statements. For example, "taking a demon ride" doesn't necessarily mean that one gets into a car and goes on a road trip with Beelzebub.

Shirley McClain is an old fraud with all that channeling bullshit. The others were "taking the piss" as it were.
You fell for it, which reenforces my belief that fundamentalist Christians have broken bullshit meters, making them vulnerable to all manner of scams.